Study of Near-Sonic Flows

对近音速流动进行了数值和实验研究。以下是本研究取得的主要成果. TAS-code是一个成熟的基于非结构网格的CFD软件，为跨音速飞机的分析和设计提供了一个实用的工程工具.开发了一个基于伴随方程的高效直接优化程序。将其应用于某跨音速飞机的翼-舱-挂架一体化优化设计，获得了重要的工程信息.采用遗传算法和数据挖掘方法，开发了一套高效的跨音速飞机多学科优化设计程序.提出了一种提高CFD阻力预测精度的新方法。利用该方法，对求解精度非常敏感的翼梢小翼的优化成为可能.利用TAS程序对马赫数为0.98的音速飞机进行了气动优化。结果表明，升阻比提高了25%，并获得了有效音速飞机的一般条件的重要知识.数值分析了跨音速再入舱的动力不稳定性趋势，提出了一种再入舱动力稳定性的预测方法.采用LES/RANS混合方法对高速飞行器底部流场进行了数值模拟。结果表明，跨音速下的时间序列特征与其它速度域有显著的不同.利用TAS程序对可重复使用空天飞机近音速升降副翼反转现象进行了数值研究，并分析了其原因。提出了防止升降副翼反转的方法.对弱激波的各种流动现象进行了实验和数值研究，以获得物理上的理解。

Numerical and experimental studies of flows at near-sonic speed have been conducted. The following are the major results obtained by this research.1. The TAS-code, an in-house unstructured-grid based CFD soft, was sophisticated and a practical engineering tool for analyzing and designing transonic airplanes was constructed.2. An efficient direct optimization code using the adjoint equation was developed. It was applied to optimize the wing-nacelle-pylon integration of a transonic airplane and an important engineering information was obtained.3. An efficient, multi-disciplinary optimization code for designing a high-performance transonic airplane was developed using the genetic algorithm and the data mining method.4. A new method to improve the prediction accuracy of the drag by CFD was developed. With this method, an optimization of winglet, which is generally very sensitive to the solution accuracy, becomes possible.5. A sonic plane at Mach 0.98 was aerodynamically optimized using the TAS-code. The result showed 25% improvement of the lift-to-drag ratio and the important knowledge of a general condition for an efficient sonic plane was obtained.6. Dynamically unstable tendency of a reentry capsule at transonic speed was numerically analyzed and a prediction method for the dynamic stability of the capsule was proposed.7. Physics of base flows of a high-speed vehicle was numerically investigated with the LES/RANS hybrid methodology. It was shown that the time-series characteristics at transonic speed was significantly different from other speed regimes.8. An elevon reversal phenomena at near-sonic speed of a reusable space plane was numerically investigated using the TAS-code and the cause was identified. The method to prevent the elevon reversal was proposed.9. Various flow phenomena of weak shock waves were experimentally and numerically investigated for the physical understanding.